Production of hydrazine



United States Patent No Drawing. Original application October 23, 1950,Se-

rial No. 191,735, now Patent No. 2,675,301, dated April 13, 1954.Divided and this application May 20, 1952, Serial No. 288,997 i f '17Claims. (01. 23-190 This invention relates to the production ofhydrazine. In one aspect, the invention relates to a method for theconversion of urea to hydrazine. This application is a division of myprior and co-pending application Serial No. 191,735 filed October 23,1950, now U. S. Patent No. 2,675,301, which is a continuation-in-part ofmy prior and co-pending application Serial No. 733,994 filed March 11,1947, now abandoned, relating to the production of hydrazine.

Hydrazine hydrate has heretofore been manufactured by reactinghypochlorite solution with ammonia, the hypochlorite solution beingprepared from sodium hydroxide and chlorine. The reactants for thepreparation of hydrazine hydrate by this method are, therefore, 2molecules of ammonia, 1 molecule of chlorine and 2 molecules of sodiumhydroxide for each molecule of hydrazine hydrate produced. It has beenfound that this method has the disadvantage that the relativelyexpensive reactants, namely, sodium hydroxide and chlorine, constituteonly intermediates in the process and are represented in theresultingproducts as relatively worthless sodium chloride and water. Aside fromthe material loss which these products represent, their presence in thereaction product is a positive disadvantage since they must beultimately separated from the hydrazine hydrate product produced.

It is an object of this invention to provide an improved method for theproduction of hydrazine.

Another object of the invention is to provide an improved method for theproduction of hyrdazine which requires no expensive reagents thatare-largely recovered in any form other than hydrazine or hydrazinehydrate.

A further object of the invention is to provide a process for theproduction of hydrazine in which the recovery of the product constitutesa relatively simple operation.

A still further object of the invention is to provide a process for theproduction of hydrazine at a unit cost substantially lower than theprior process referred to above.

Other objects and advantages inherent in the invention will becomeapparent from the following description.

In accordance with the improved process of the present 7 2,7 17,201Patented Sept. 6, 1955 at least such quantity of thecarbonyl-forming'metal must be used to produce readily isolatableamounts of hy drazine. However, it is preferred that the'carbonylforming metal be :present in an amount of at least 10 weightper cent of the urea present in the reaction zone, while an amount ofthemetal equivalent to at least 50 weight percent of theurea presentin'the reaction zone invention, hydrazine is produced by contacting ureaunder suitable conditions with a carbonyl-forming metal such as nickel,iron, cobalt, ruthenium, molybdenum, chromium and tungsten. Of thesecarbonyl-forming metals, nickel is preferred for carrying out theprocess of the invention when employing a relatively low temperature, asmore fully hereinafter described, while iron is preferred when carryingout the process of the invention at relatively higher temperatures. Y

The reaction is carried out by contacting urea under proper reactionconditions with the carbonyl-forming metal which is present in an amounteffective to conhas been found to be most efiective in carrying out thehydrazine producing reaction.

. The above reaction is preferably carried out by contacting urea withthe carbonyl-forming metal at tempera}- tures between about 40 C. andtemperatures just below the temperature of decomposition of urea. Thedecomposition of urea takes place between about 132,C. and about C. Itis within the scope of the invention to. carry out the reaction attemperatures at which decomposition of urea takes place, or attemperatures above the temperature of decomposition of urea; however,from a standpoint of economics; such temperatures are not preferred. V

In accordancepwith one modification of the invention, the urea iscontacted while in a molten condition with the carbonyl-forming metal,such as nickel or iron. In accordance with this modification, it ispreferred to operate above 132" C. and just below the'temperature ofsubstantial decomposition of the urea. The molten urea is flowedthrough'a granular mass of the nickel or iron at atmospheric pressure.The heat of reaction is supplied, primarily, by the molten urea, butadditional heat is .sup-

plied by indirect heat exchange, if necessary, to maintain a employed,some carbonyls may be formed but these are readily decomposed to carbonmonoxide and iron. Some iron penta-carbonyl may-be formed which mayreact with hydrazine and other reactants present to form a complex whichdecomposes to semicarbazide and iron tetra-carbonyl. These compounds arereadily separated from hydrazine at temperatures above 113 C. Theformation of the semicarbazide represents a consumption of, at most,one-fifth of the available urea. This cannot be considered as a loss,however, since semicarbazide is a valuable product.-

p In the above described modification, the iron or nickelcarbonyl-forming metal functions as a true catalyst in that no stablemetal compounds are formed, the principal products being hydrazine andcarbon monoxide. If any metal-carbonyl is formed, it is rapidlydecomposed at the relatively high reactiontemperature. Under theseconditions, the formation of semicarbazide or hydrazine dicarbonamide isminimized. When employing iron as the carbonyl-forming metal, arelatively high temperature, as indicated above, is necessary tomaintain this condition. Such temperatures are also effective for theuse of nickel as the carbonyl-forming metal. It should be noted,however, that temperatures below the melting point of urea may beeffectively employed with nickel. This condition may be maintained withnickel at temperatures between about 60 C. and about 70 C. or higher.

In accordance with another modification of the invention, the contact ofurea with the carbonyl-forming metal is effected at temperatures belowthe melting point of urea and at which the metal carbonyl is relativelystable. Under these conditions, nickel is preferably employed as thecarbonyl-forming metal and temperatures within the range of about 40 C.to about 60 C. are utilized. It is preferred to employ a substantialexcess of the nickel.

Contact may be eliected by intimately mixing nickel powder with powderedurea. The nickel having been previously heated to a temperaturesufiiciently high to heat the urea to the desired temperature and supplythe heat of reaction. Liquid hydrazine is formed by this operation,while nickel carbonyl is produced as a gaseous reaction product. Theterm hydrazine is employed throughout this specification for the sake ofconvenience, but is intended, unless otherwise indicated, to include notonly anhydrous hydrazine itself, which is produced for the most part inaccordance with the present process, but also hydrazine hydrate as well.

The above reaction may be represented, in general, by the followingequation in which nickel is employed as a representativecarbonyl-forming metal:-

The thus formed carbonyl is then decomposed to carbon monoxide and themetal, which may be represented by the following equation:

The procedure for the recovery of the hydrazine product will depend uponthe reaction conditions employed. When the reaction zone is maintainedat a temperature above the melting point of urea, gaseous hydrazine andcarbon monoxide are the principal efiiuents. Some semicarbazide and irontetracarbonyl may be formed, but these are readily separated by coolingthe efliuents to temperatures at which the hydrazine remains in thevapor form. The mixture of hydrazine and carbon monoxide is thenfractionated in a suitably packed fractionating tower to yield ahydrazine product essentially free from metal carbonyls.

In instances where the reaction temperature is below the melting pointof urea but above the boiling point of hydrazine, the principal gaseouseffluent is gaseous hydrazine, although some carbon monoxide may bepresent and some iron carbonyl may remain with unconverted solid urea.The effluent vapors are freed from iron carbonyl by being heated totemperatures between about 140 C. and about 150 C.

When reaction temperatures below the boiling point of hydrazine areemployed, the gaseous effluent is essentially carbon monoxide. Thisgaseous efiiuent may also include metal carbonyl vapors, depending uponthe particular metal employed and upon the reaction temperature. Whennickel is employed at a relatively low temperature, nickel carbonylvapors may be present in the effiuent gas in greater quantity thancarbon monoxide. The liquid hydrazine product and accompanying unreactedurea is removed from the reaction zone and maintained at a temperaturebetween about 60 C. and about 80 C. for approximately to 60 minutes todecompose nickel carbonyl. The product is then separated from any nickelwhich has settled out and is then distilled, preferably by flashdistillation, to remove hydrazine as rapidly as possible from unreactedurea. Unreacted urea and recovered nickel catalyst may then be recycledto the operation. It will be understood that when the gaseous effluentcomprises largely nickel carbonyl, this material is separately heated toa temperature above the decomposition temperature of nickel carbonyl torecover nickel for reuse as a catalyst.

Preferably the reaction is carried out at low pressure, for example,atmospheric pressure or slightly higher pressure, as high pressureapparently causes the hydrazine product to react with urea withresulting loss of hydrazine.

Having thus described my invention, I claim:

1. A method for producing hydrazine which comprises: contacting ureawith a particulate carbonyl-forming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 2 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between about 40 C. andbelow the melting point of urea to convert at least a substantialquantity of urea present to hydrazine; and recovering hydrazine as aproduct of the process.

2. A method for producing hydrazine which comprises: contacting ureawith a particulate carbonyl-forming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 10 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between about 40 C. andbelow the melting point of urea to convert at least a substantialquantity of urea present to'hydrazinc; and recovering hydrazine as aproduct of the process.

3. A method for producing hydrazine which comprises: contacting ureawith a particulate carbonyl-forming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 50 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between about 40 C. andbelow the melting point of urea to convert at least a substantialquantity of urea present to hydrazine; and recovering hydrazine as aproduct of the process.

4. The process of claim 3 in which the carbonylforming metal is iron.

5. The process of claim 3 in which the carbonylforming metal is nickel.

6. The process of claim 3 in which the carbonylforming metal is cobalt.

7. The process of claim 3 in which the carbonylforming metal ismolybdenum.

8. The process of claim 3 in which the carbonylforming metal istungsten.

9. A process for producing hydrazine which comprises: contacting ureawith a particulate carbonyl-forming metal in a reaction'zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 2 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between about 40 C. andthe boiling point of hydrazine to convert at least a substantialquantity of urea present to hydrazine; and recovering hydrazine as aproductof the process.

10. A process for producing hydrazine which comprises: contacting ureawith a particulate carbonylforming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 2 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between the boilingpoint of hydrazine and below the melting point of urea to convert atleast a substantial quantity of urea present to hydrazine; andrecovering hydrazine as a product of the process.

11. A process for producing hydrazine which comprises: contacting ureawith a particulate carbonylforming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 2 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between about 40 C. andthe boiling point of hydrazine to convert at least a substantialquantity of urea present to hydrazine and produce a mixture comprisingliquid hydrazine and a metal carbonyl and a gaseous phase comprisingcarbon monoxide; and recovering hydrazine from the remaining products ofreaction.

12. A process for producing hydrazine which comprises: contacting ureawith a particulate carbonylforming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 2 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between the boilingpoint of hydrazine and below the melting pointof urea to convert atleast a substantial quantity of urea present to hydrazine and produce agaseous effluent comprising hydrazine; and recovering hydrazine fromsaid effiuent.

13. A process for producing hydrazine which comprises: contacting ureawith a particulate carbonylforming metal in a reaction zone, saidcarbonyl-forming metal being continuously maintained in an amountequivalent to at least 2 per cent by weight of the quantity of ureapresent in said reaction zone, at a temperature between about 40 C. andthe boiling point of hydrazine to convert at least a substantialquantity of urea present to hydrazine and to produce an efiluentcomprising liquid hydrazine and a metal carbonyl and a gaseous phasecomprising carbon monoxide; withdrawing liquid hydrazine and metalcarbonyl from said reaction zone; regenerating the metal from said metalcarbonyl; and contacting said regenerated metal with further quantitiesof urea.

14. A process for producing hydrazine which comprises: contacting ureawith nickel particles in a reaction zone, said nickel particles beingcontinuously maintained in an amount equivalent to at least 2 per centby weight of the quantity of urea present in said reaction zone, at atemperature between about 40 C. and about 60 C. to convert at least asubstantial quantity of urea present to hydrazine and to produce aneflluent comprising liquid hydrazine and nickel carbonyl and a gaseousphase comprising carbon monoxide; withdrawing liquid hydrazine andnickel carbonyl from said reaction zone; regenerating nickel from saidnickel carbonyl; and contacting said regenerated nickel with furtherquantities of urea.

15. A process for producing hydrazine which comprises: contacting ureawith nickel particles in a reaction zone, said nickel particles beingcontinuously maintained in an amount equivalent to at least 2 per centby weight of the quantity of urea present in said reaction zone, at atemperature between about 40 C. and the boiling point of hydrazine toconvert at least a substantial quantity of urea present to hydrazine andto produce an eflluent comprising liquid hydrazine and nickel carbonyland a gaseous phase comprising carbon monoxide; withdrawing liquidhydrazine and nickel carbonyl from said reaction zone; maintainingliquid hydrazine and nickel carbonyl r'thus withdrawn at a temperaturebetween about 60 C.

ate nickel from said nickel carbonyl; and contacting said regeneratednickel with further quantities of urea.

16. A process for producing hydrazine which comprises: contacting ureawith nickel particles in a reaction zone, said nickel particles beingcontinuously maintained in an amount equivalent to at least 2 per centby weight of the quantity of urea present in said reaction zone, at atemperature between about 40 C. and about 60 C. to convert at least asubstantial quantity of urea present to hydrazine and to produce anefiluent comprising liquid hydrazine and nickel carbonyl and a gaseousphase comprising carbon monoxide; withdrawing liquid hydrazine andnickel carbonyl from said reaction zone; maintaining liquid hydrazineand nickel carbonyl thus withdrawn at a temperature between about C. andabout C. for a residence time between about 10 minutes and about 60minutes to decompose and regenerate nickel from said nickel carbonyl;and contacting said regenerated nickel with further quantities of urea.

17. A method for producing hydrazine which comprises contacting ureawith nickel particles in a reaction zone, said nickel particles beingcontinuously maintained in an amount equivalent to at least 2 per centby weight of the quantity of urea present in said reaction zone, at atemperature between about 40 C. and below the melting point of urea toconvert at least a substantial quantity of urea present to hydrazine;and recovering hydrazine as a product of the process.

References Cited in the file of this patent UNITED STATES PATENTS2,129,689 Hetherington Sept. 13, 1938 2,527,315 Mackay Oct. 24, 1950

1. A METHOD FOR PRODUCING HYDRAZINE WHICH COMPRISES: CONTACTING UREAWITH A PARTICULATE CARBONYL-FORMING METAL IN A REACTION ZONE, SAIDCARBONYL-FORMING METAL BEING CONTINUOUSLY MAINTAINED IN AN AMOUNTEQUIVALENT TO AT LEAST 2 PER CENT BY WEIGHT OF THE QUANTITY OF UREAPRESENT IN SAID REACTION ZONE, AT A TEMPERATURE BETWEEN ABOUT 40* C. ANDBELOW THE MELTING POINT OF UREA TO CONVERT AT LEAST A SUBSTANTIALQUANTITY OF UREA PRESENT TO HYDRAZINC; AND RECOVERING HYDRAZINE AS APRODUCT OF THE PROCESS.